1. Field of the Invention
The present invention relates to a method for making a flexographic printing master by inkjet printing and an imaging apparatus for performing the method.
2. Description of the Related Art
Flexography is commonly used for high-volume runs of printing on a variety of supports such as paper, paperboard stock, corrugated board, films, foils and laminates. Packaging foils and grocery bags are prominent examples.
Today flexographic printing forms are made by both analogue imaging techniques such as a UV exposure through a film mask, e.g. EP 1594005 (DUPONT), and digital imaging techniques which include:                direct laser engraving on flexographic printing form precursors, e.g. US 2004/0259022 (BASF);        UV exposure through a LAMS mask, e.g. U.S. Pat. No. 6,521,390 (BASF) and U.S. Pat. No. 7,226,709 (KODAK), wherein LAMS means Laser Ablative Mask System;        Mask-less direct UV or violet exposure by laser or LED, e.g. U.S. Pat. No. 6,806,018 (MACDERMID); and        Inkjet printing e.g. EP 1428666 A (AGFA), US 2004/0131778 A (AGFA) and US 2006/0055761 (AGFA).        
EP 1428666 A (AGFA) discloses a method for making a flexographic printing form by jetting subsequent layers of a UV-curable liquid, having elastomeric properties after being cured. Before jetting the following layer each previous layer is immobilized by a UV curing step. This “layer after layer” recording technique allows the gradual building up of a flexographic printing master wherein the relief can be accurately controlled. Use can be made of different curable liquids or immobilisation steps to obtain different layer characteristics.
Advantages of such a method for preparing a flexographic printing master are the absence of any processing steps and the consumption of no more material as necessary to form a suitable relief image, i.e. the removal of non printing areas is no longer required.
However, it has been observed that inkjet printed flexographic printing masters are more susceptible to damage during the handling before flexographic printing. Also during printing very small printing dots on the flexographic printing master can break off.
A need exists for making flexographic printing masters by inkjet printing in a short manufacturing time, which exhibit high printing quality and are less susceptible to damage.